The beam breakup instability (BBU) and THz radiation-driven thermal loading of free electron laser (FEL) mirrors are well-characterized performance limitations in high power free electron laser (FEL) systems. Such systems are, further, often based on topologies that use laser optical elements embedded within the driver accelerator footprint, necessitating the use of magnetic dipole elements to separate the electron drive beam from the optical mode axis and direct it away from and/or around said optical components. Momentum compaction managed systems used for the temporal compression of charged particle beam bunches also frequently use similar magnetic transport—such as a chicane—to provide path-length/momentum correlations needed for the bunch compression process.
The accelerator transport elements required to address each of these issues have, in the prior art, been of separate functionality and have been installed in separate regions of the driver accelerator. BBU has been effectively addressed through the use of a skew-quad eigenmode exchange module (SQEEM [D. Douglas, “A Skew-Quad Eigenmode Exchange Module (SQEEM) for the FEL Upgrade Driver Backleg Transport”, JLAB-TN-04-016, 12 May 2004]) wherein a system of five symmetrically arrayed skew quadrupoles are powered in three families, thereby providing a complete and betatron stable cross-coupling of the transverse motion. THz loading of mirrors has been effectively suppressed through the use of a magnet dipole chicane between the wiggler and the downstream FEL optical element as described in a copending patent application. In the prior art, interferences between electron drive beam and optical systems are often resolved through the use of an additional magnetic chicane, wherein the electron beam is directed around the optical elements under consideration and/or merged with or separated from the optical mode as is required. Similarly, beam bunching can be provided through the appropriate use of a dipole magnet chicane.
Each of these systems individually requires approximately the same spatial footprint (for a 100 MeV electron beam, this would be of the order of a few to 10s of m2); their use via independent installation thus subsumes some factor as large as two (or more) times as much space as would a more integrated approach. Thus there is a need to somehow consolidate these functionalities so as to reduce the footprint of the overall installation.